A phase interpolator outputs periodical signals based on a set of reference signals and a control signal. The control signal controls the phases of the output signals, and is typically a digital signal. A phase interpolator with a digital control signal produces output signals having discrete phases. Phase interpolators may be used in a variety of systems, such as radio frequency (RF) receivers, and Plesiochronous or Mesochronous communications systems.
Injection-lock refers to a phenomena when a first signal is coupled to a second signal while the two signals having similar but different frequencies (or phases), the coupling may cause the frequency (or phase) of the second signal to be essentially identical to the frequency (or phase) of the first signal.